The long-term purpose of this proposal is the identification of the trophic substances that determine the trophic influences of the neuronal cell body on the axon and on its end organs. This can be done by developing a rigorous bio-assay where the end point is quantitative and based on the behavior of individual, identical and identifiable neurons in organ culture of mature nervous systems of amphibians and/or crustaceas. The immediate objectives are: 1) To develop organ culture preparations (particularly the crayfish nerve cord-neuromuscular preparation) where it will be possible to follow continuously the events related to degeneration at a cellular level, by means of intracellular recordings, time lapse cinematography and automatic morphometric methods. 2) To quantitatively monitor the events that occur after axotomy in such organ cultures. 3) To discriminate between the signs due to cell membrane injury and those due to degeneration. 4) To determine the roles of synaptic inputs (particularly electrical synapses) in the process of degeneration and cell to cell passage of trophic substances. 5) To find out whether it is possible to prevent or reverse the signs of degeneration by means of intracellular injection or extracellular application of putative trophic substances. 6) To study the mechanisms of sealing off injured axonal membranes (axonal sealing) and the factors that act upon it.